Even in a pro-business setting like the Detroit Athletic Club, a utopian vision to remake Belle Isle as an independent commonwealth ran into healthy skepticism Monday.

Sandy Baruah, president and CEO of the Detroit Regional Chamber, told developer Rodney Lockwood and his partners that they hadn’t done enough to explain how their idea for a wealthy, virtually tax-free enclave on Belle Isle would benefit Detroit itself.

George Jackson, president and CEO of the Detroit Economic Growth Corp., dismissed the Lockwood vision as “trickle-down” economics that held few benefits for the city itself.

And Gary Brown, a member of Detroit’s City Council, told the Lockwood partners that visionary plans like theirs only work if you tackle the problems of the city first, that their plan provided no fix for the city’s ills.

But the Commonwealth of Belle Isle idea found several supporters, too, among the invited guests at the DAC. John Rakolta, chairman and CEO of the Walbridge construction firm based in Detroit, said the Lockwood vision could produce $20 billion in new investment and create 200,000 jobs in the city in 10 years, although he admitted the numbers were just guesses.

Meanwhile, both Jackson and Brown said they expected the State of Michigan and City of Detroit to agree next week on a deal to have Belle Isle become a state park. Brown said the final issue appears to be which agency will provide security patrols.

That vision is less a detailed plan than a concept contained in a fictional book by Lockwood set years in the future, after the commonwealth has transformed both the island and the city.

That vision leans heavily on the free-market premises found in the work of the late author Ayn Rand. A low-tax, low-regulation commonwealth on Belle Isle would be free of crime, inflation and public corruption, the partners said.